Common lubricants for bearings:
Lubricating oil -- liquid, most widely used;
Grease - semi solid, generally used at medium and low speed;
Solid lubricant: an additive mainly used as oil and fat, or used alone.
Performance selection of lubricating oil:
Viscosity - Indicates the amount of internal friction resistance in a flowing liquid.It is the most important performance index and the main basis for selecting lubricating oil.
Oily property, also known as lubricity, characterizes the ability of polar molecules in oil to adsorb metal surfaces.Good oil leads to low friction coefficient.
Condensation point -- reflects the low temperature performance of lubricating oil.
Flash point - reflects the high temperature performance of lubricating oil.
The selection principle of lubricating oil:
1, high pressure or in the impact, variable load conditions work, should choose oil with high viscosity;
2, when the speed is high, the oil with low viscosity should be selected to reduce friction loss;
3, when the working temperature is high, the oil with high viscosity should be selected, because the viscosity will decrease with the rise of temperature.
Performance selection of grease:
Needle penetration -- represents the thin consistency of a grease, similar to the viscosity of an oil;
Dropping point -- represents the high temperature resistance of grease.
The selection principle of grease:
1, the working environment has water vapor, choose calcium based grease;
2, high working temperature, sodium base grease;
3, there is water vapor and the working temperature is high, lithium grease should be selected.
Solid lubricant: in order to prevent and protect the friction surface in the relative movement from damage and reduce its friction and wear on the surface of the use of powdered or thin film solid lubricant.Solid lubricant has a wide range of temperature, strong bearing capacity, good anti-stick-slip, high vacuum resistance, radiation resistance, wide range of electrical conductivity, corrosion resistance and dustproof, so it is a special kind of lubricant.The disadvantage is that the friction coefficient is generally greater than the lubricating grease, the energy loss is greater;Can not play a cooling role;The membrane process is complex.